I have a no start 87 F250 (5.0). Suspect ECM but want to pinpoint first if possible. I can't get error codes from ECM. I have no elec power to fuel pumps, althought they will operate if connected directly. There is no power at any time to the EEC relay and power at all times (Yellow wire only) to the fuel pump relay. No additional power w/key on to either relay. Checked inertia switch and fusible links at elec solenoid. All OK. No initial 2 second power either.
Does EEC relay pick up power from ignition switch, solenoid, or ECM/ What color wire? Grounding fuel pump term on access plug also no response. Does fuel relay receive signal from EEC relay or ECM unit? Also no signal from pin #37 on ECM.
HELP!

 

I don't think it is the computer. There should be a wire on the ECM relay that is hot all the time. The ECM controls the fuel pumps, so if the ECM is not turning on, then the fuel pumps will not be switched either.

 

Any idea which wire should be "hot"? and where it picks up power at. I could follow it back to detect any break.

 

Well, the yellow wire on the EEC relay should stay 12V all the time. Black is a ground, and the white/light blue is hot when the key is on. I think the power goes back to the starter solonoid where there are fusible links, but I don't know for sure. According to my wiring diagram, the yellow supply power wire on the Fuel pump relay is only hot with the key on, but that doesn't make sense, because it also goes to the keep alive power for the computer which should stay on.

 

My yellow to the fuel relay is always hot, but not to the EEC. Since all fuse link test OK, I assumed that EEC picked up power from ECM unit, but perhaps have break in line somewhere else. Would it perhaps pick up power from the ignition switch?

 

That's how the wiring diagram reads - the yellow on the ECM relay is hot with the ignition turned on. The EEC relay powers the ECM and all the engine control solonoids and injectors.

 

Thanks, will recheck wiring and be certain I have power to the EEC relay first before blaming the ECM unit